2,5-Dimethylphenylacetic acid is an important intermediate of fine chemical industry. It is widely used in the fields of medicine and pesticide, and especially, it is a key intermediate of the novel pesticide called spirotetramat which, is the only pesticide with bi-directional systemic transmission function so far.
Several main methods in synthesizing 2,5-dimethylphenylacetic acid referred to the domestic and overseas literatures are as follows:
1. In Bulletin of the Chemical Society of Japan 1975, 48(2), 497-504, the 2,5-dimethylphenylacetic acid was synthesized by a two-step reaction of cyaniding and hydrolyzing with the starting reactant 2,5-dimethylbenzyl chloride by Kazuhiko et al. The synthetic route was as the following:

2. The synthetic method of 2,5-dimethylphenylacetic acid which was disclosed, in Bayer's patent CN1918103 was to transform the p-xylene into 2-chloro-1-(2,5-dimethylphenyl)ethanone(I) with chloroacetyl chloride, transform the said ketone into the corresponding ketal(III) with the diol(II), and then rearrange the ketal(III) to give the mixture of 2,5-dimethylphenylacetic acid hydroxyalkyl ester(IV) and bis(2,5-dimethylphenylacetic acid) diester(V). Finally, the said mixture was hydrolyzed to give 2,5-dimethylphenylacetic acid. The synthetic route was as the following:

3. A process for preparing 2,5-dimethylphenylacetic acid, in which 2,5-dimethylphenylacetic acid was synthesized by undergoing coupling and hydrolyzing reactions with the starting reactant 1-(2,5-dimethylphenyl)ethanone, was disclosed by Daicel in patent JP2008291008. The synthetic route was as the following:

In conclusion, all the processes above have the problems that the raw materials are expensive, synthetic routes are long and the types of reactions are complicated.